EGFR variant III (EGFRvIII), a tumor specific mutant of EGFR, is a product of genomic rearrangement which is often associated with wild-type EGFR gene amplification. EGFRvIII is formed by an in-frame deletion of exons 2-7, leading to deletion of 267 amino acids with a glycine substitution at the junction. The truncated receptor loses its ability to bind ligands but acquires constitutive kinase activity. Interestingly, EGFRvIII always co-expresses with full length wild-type EGFR in the same tumor cells. Moreover, EGFRvIII expressing cells exhibit increased proliferation, invasion, angiogenesis and resistance to apoptosis.
EGFRvIII is most often found in glioblastoma multiforme (GBM). It is estimated that 25-35% of GBM carries this truncated receptors. Moreover, its expression often reflects a more aggressive phenotype and poor prognosis. Besides GBM, expression of EGFRvIII has also been reported in other solid tumors such as non-small cell lung cancer, head and neck cancer, breast cancer, ovarian cancer and prostate cancer. In contrast, EGFRvIII is not expressed in healthy tissues. The lack of expression in normal tissues makes EGFRvIII an ideal target for developing tumor specific targeted therapy.
Adoptive transfer of T cells genetically modified to recognize malignancy-associated antigens has shown promise as a new approach to treating cancer (see, e.g., Brenner et al., Current Opinion in Immunology, 22(2): 251-257 (2010); Rosenberg et al., Nature Reviews Cancer, 8(4): 299-308 (2008)). T cells can be genetically modified to express chimeric antigen receptors (CARs), which are fusion proteins comprised of an antigen recognition moiety and T cell activation domains (see, e.g., Eshhar et al., Proc. Natl. Acad. Sci. USA, 90(2): 720-724 (1993), and Sadelain et al., Curr. Opin. Immunol, 21(2): 215-223 (2009)). Accordingly, treatment to a solid tumor such as glioblastoma multiforme using an anti-EGFRvIII antagonist including EGFRvIII specific CARs and EGFRvIII specific CAR-T cells would make a promising therapeutic agent.